Various approaches may be used to identify cylinder stroke in the engine firing order independent from camshaft information. In one example, manifold pressure may be used to identify cylinder stroke.
The inventors herein have recognized that such approaches may be inaccurate, especially during conditions in which the engine speed is low (such as during very low ambient temperature conditions and/or during weak battery conditions). Such inaccuracies may be especially difficult in direct injection engines, since fuel may be delivered at least partially during an expansion and/or compression stroke, in which case unburned fuel may be delivered to the exhaust without combustion.
As such, in one example, a method for starting an internal combustion engine may be used, the method comprising identifying cylinder stroke during the engine start responsive to a fuel rail pressure. In one particular example, the fuel rail pressure may be used during open fuel injector operation with the fuel pressure above ambient pressure, but below cylinder compression pressure near TDC. In this way, by monitoring whether the fuel rail pressure increases or decreases when the fuel injector is opened near TDC of the cylinder in which the injector is located, the stroke may be identified. For example if fuel rail pressure increases, then the stroke corresponds to TDC compression, but if it decreases, then the stroke corresponds to TDC exhaust. Note that this is just one example approach, and various others may be used.